Electro-magnet based telescoping artificial muscle actuator

ABSTRACT

The device described herein is an Electro-magnet based Telescoping Artificial Muscle Actuator. This device uses a centrally located electromagnet which acts on permanent magnets and ferrous components housed within telescoping sections of this device. This device is intended to be linked into chains of other identical devices, with those chains then linked into bundles. This arrangement allows devices of this type simulate the action and control mechanisms of natural muscle. This device is intended for use in prosthetic, robotic, and implantable applications.

US REFERENCES

U.S. Pat. No. 6,781,284 (2004 Aug. 24) Ronald E. Pelrine, Electroactivepolymer transducers and actuatorsU.S. Pat. No. 6,223,648 (2001 May 1) Joel R. Erickson, Artificial muscleactuator assembly20070186712 (2007 Aug. 16) Carlo Ferraresi, Double-acting deformablefluid actuator of the muscle type with three chambers20070193267 (2007 Aug. 23) Xinhua Sam He, Electrical actuator havingsmart muscle wireU.S. Pat. No. 6,960,847 (2005 Nov. 1) Yuzuru Suzuki, Electromagneticactuator and composite electromagnetic actuator apparatusU.S. Pat. No. 4,703,297 (1987 Oct. 27) Nagahiko Nagasaka, Permanentmagnet type linear electromagnetic actuator

FOREIGN REFERENCES

WO/1997/027822 (1997 Aug. 7) John Chilver, Artificial muscle

BACKGROUND OF THE INVENTION

The field to which this invention pertains is to that of prosthetic androbotic motor systems and functional soft tissue biomechanical implants.Current prosthetic devices employ rotary servos controlled by computersystems (1). These servos require computers to adapt signals coming froma body into appropriate control of rotary servos. These apparatus'require heavy batteries and do not provide the dexterity or in mostcases the strength of a biological motor system (2). These drawbacksstem mostly from attempts to adapt robotic system to biological ones,which are more robust, power efficient and accurately controlled by thebody. Current artificial muscle devices, meant to more effectivelysimulate the action of natural muscles, have been developed utilizingcompressed air bladders and contractile polymers. These systems arestill largely experimental and present significant drawbacks.Contractile polymer systems do not provide sufficient strength incurrent applications to replicate natural functioning (3). They alsorequire computer control systems. Air bladder muscles, although strongand effective, still require computer control systems as well as powerfor air compressors (4). There are currently no technologies capable ofbeing implanted in a living body to effectively replace a damaged orremoved natural muscle.

BRIEF SUMMARY OF THE INVENTION

This invention, an Electro-magnet based Telescoping Artificial MuscleActuator, is intended to address the drawbacks of the previous art inseveral ways. Firstly, this device is intended to be used in eitherprosthetic, robotic or implant technologies. Secondly, this device isintended to be used with a control system that can directly convertbiological control signals to comparable actuation control.

The actuator described herein is intended to be a modular component of alarger muscle system. This device is a simple spring loaded armaturewith a core electromagnet which powers contraction. This device isintended to be controlled primarily be an all or nothing control signal.Each control signal received by this device powers its activitydirectly. Each actuator is intended to be joined end to end to otheridentical actuators, which each addition providing additional power ofcontraction. These assemblies are intended to then be grouped with othersimilar chains of actuators. Control of such an apparatus would beaffected through the number of chains of actuators being activated aswell as the frequency of control signals received. This control systemis akin to that of biological muscle and should be able to processsignals directly from the body. This could be done using a direct nerveinterface, conventional myoelectric detection, or myoelectric controlsystems in conjunction with nerve/muscle graft surgeries. Each actionpotential that would be sent to a natural muscle group, would activatethe power supply of a specific actuator chain. The addition of signalsfrom complimentary muscle groups would activate additional actuatorchains.

Power to this system would ideally be supplied through the use of highvoltage capacitor banks linked to kinetic chargers; however appropriatebattery and stationary charger systems are acceptable. These actuators,in their chain and bundle arrangement, are intended to be usedexternally in prosthetic devices or in robotic applications. Theseactuators, in their chain and bundle arrangements, are intended to beused as biological implants if contained within an appropriate flexiblebiocompatible sheath with sections that allow for attachment to existingtendons and/or bones. The implantable application of this device shouldbe used in conjunction with internal capacitor and control systems andexternal power storage and generation systems.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

Device contracted (FIG. 1 A). Device Extended (FIG. 2 A).Cross-sectional View of Extended Device (FIG. 2 B). Cross-sectional Viewof Contracted Device (FIG. 1B). View of actuator components linked in achain (FIG. 3). View of actuator chains grouped into a bundle (FIG. 4).

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiment of this device is as follows. The centralcomponent of this device is a solid ferrous core electromagnet (1). Thissolid core should be spindle shaped. This electromagnet should be housedin a nonferrous casing (2) that allows for attachment of the two partsof telescoping component 1 (3). Each part of component 1 (3) should bemirrored around the central electromagnet and be fitted into theelectromagnet housing by the use of screw threads or with screws withcorresponding countersunk threaded holes. Power leads (4) for theelectromagnet (1) should pass through the electromagnet housing andother components. All telescoping components of this device occur inpairs mirrored around the central electromagnet.

Component 1 (3) is open at one end with a small lip protruding towardsthe center of the opening. This lip is meant to stop the motion oftelescoping component 2 (5) by making contact with the permanent magnetbase (6) of component 2. Component 1 (3) must have a lip facing awayfrom its opening to prevent motion of telescoping component 4 (9).Component 2 (5) is housed inside component 1 (3).

Component 2 (5) is comprised of a nonferrous hollow cylinder with apermanent magnet (6) attached to one side and with the other left openwith a small lip protruding towards its center to contain telescopingcomponent 3 (7). The polarity of the permanent magnet of component 2 (5)should be oriented opposite to the polarity of the central electromagnet for each mirrored component. The surfaces of the magnets (6) ofcomponent 2 (5) which face each other should have opposing polarities.Contained within component 2 (5) is telescoping component 3 (7). Thiscomponent is solid, ferrous, and has a threaded end (8) that extendsbeyond the open end of component 2 (5).

Component 3 (7) has a lip at one end that contacts the lip of component2 (5). Component 3 (7) is not an identical mirrored pair. One unit wouldhave internal threads at the end protruding beyond component 2 (5), andone would have external threads extending to the same distance. Thisorientation, along with the threads (11), of telescoping component 5(10) allows actuators of this type to be joined together, end to end,into long chains (FIG. 3), to allow for increased force of contraction(to be discussed in detail below). Component 5 (10) is a nonferroushollow cylinder which has one end that extends to the height ofcomponent 3 (7). Each of the units of component 5 (10) would haveoppositely oriented threads (11) extending from the height of components1, 2 and 4, to the height of component 3. Its opposite end has aninternal lip that contacts telescoping component 4 (9). Component 4 (9)has a lip facing outward at its end closest to the threaded region ofthe device. It has a lip facing the center of the device which contactscomponent 1 (3). There is a spring providing compression resistance inbetween components 5 and 4 (13). Component 4 (9) is located insidecomponent 5 (10). It has a lip facing the center of the device whichinteracts with the outer lip of component 1 (3). There is a springlocated between component 4 and component 1(12).

Connections to a power source should be a simple positive/negative plugthat passes in between all outer telescoping layers and does notinterfere with their contraction. This plug should be built into thehousing of the central electro magnet.

Threaded regions do not occur in mirrored pairs. One should have a malethread and one a female to allow for actuators to be connected end toend.

The preferred dimensions of this device are that the central magnetshould have a sufficient number of coils to produce at least 0.5 to 1 lbof force. The length of this device should be anywhere from one to oneand a half times its diameter when contracted fully. The contractedlength to width ratio pictured in FIGS. 1A and 1B is 1:1. The devicepictured in all figures has a diameter of 2 cm. Dimensions of thisdevice should be varied depending on the specific application for whichit is used. This device must be capable of contracting to at least onehalf of its full extended length. This device must resist contractionand tend to return to its contracted state if no internal or externalforces are applied.

Each actuator of this type is intended to be joined end to end withother similar actuators, forming actuator chains (FIG. 3). Furtherbundling of these actuator chains (FIG. 4) is necessary to provideeffective control of contraction strength and length. Increasing theamplitude of current supplied to this device will increase itscontractile strength. Increasing the frequency of signals to this deviceaccounts for an increase in duration and degree of contraction, witheach signal control resulting in an all or nothing action of theactuator. Additional units to a chain of actuators and additions ofactuator chains are intended to be the principle method of increasingthe functional strength of contraction generated by this type ofactuator.

Order of assembly of this device is as follows: Telescoping component 3is fitted into the cylindrical portion of telescoping component 2, andthen the magnet (6) is attached to component 2. Components 2 and 3 areinserted into telescoping component 1. A spring (13) is then fittedaround component 1. Component 1 is then fitted into telescopingcomponent 4. A spring (12) is then placed around component 4. Component4 is then fitted into telescoping component 5. This should be done foreach mirrored section of telescoping components, and then component 1 ofeach mirrored pair should be attached to the electromagnet housing (2).

Actuator components can then be secured into long chains by means ofthreads.

Chains of actuators should be bundled together to create an artificialmuscle apparatus (FIG. 4). The strength of contraction of these bundlesis dependent upon the amplitude of current supplied to each actuator,the number of actuators in a chain, and the number of chains in thebundle which are activated. Duration of contraction (and length ofcontraction, depending on the load on the system) is dependent upon thenumber of control signals received per unit time. Bundles of chains ofactuators may be linked together by their ends to create a singlecontractile unit. A unit of this nature should be surrounded by aflexible, biocompatible, sheath (14, shown as a cut-away) to allow forimplantation. This sheath should have terminal components (15) that canbe affixed to biological structures (such as tendons or bones), as wellas to the ends of the contractile unit.

Components of this device should be manufactured using standard millingand/or injection molding techniques.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGCOMPACT DISC APPENDIX

Not Applicable

CITATIONS

-   -   (1) Carroll, Kevin (2006). Prosthetics and Patient Management: A        Comprehensive Clinical Approach. SLACK Incorporated. ISBN        1556426712, 9781556426711    -   (2) Ibid    -   (3) U.S. Pat. No. 6,781,284 (2004 Aug. 24) Ronald E. Pelrine,        Electroactive polymer transducers and actuators    -   (4) U.S. Pat. No. 6,223,648 (2001 May 1) Joel R. Erickson,        Artificial muscle actuator assembly

OTHER REFERENCES

-   Anthony, Catherine Parker (1975). “Textbook of Anatomy and    Physiology” 9^(th) edition. C.V. Mosby Company-   Gray, Henry (1930). “Anatomy of the Human Body” 22^(nd) edition.    Philadelphia: Lea and Febiger-   Martini, Frederic H. (2009). “Human Anatomy” 6^(th) edition. San    Francisco: Pearson Education-   Silverthorn, Dee Unglaub (2007). “Human Physiology: An integrated    approach” 4^(th) edition. San Francisco: Pearson Cummings

1. This device will generate contractile force through the use of anelectromagnet acting upon permanent magnets and ferrous componentsreflected around said central electromagnet. Permanent magnet componentsmust be oriented to generate an attractive force between them and theelectromagnet. Contraction of this device is all or nothing, with eachcontrol signal supplying the power for a single contraction. Power ofthis device can be increased by increasing the amplitude of currentsupplied to the electromagnet. This device will have a contracted lengthat least one half of its fully extended length. Duration of contractionis a function of the frequency of command signals received. Compressionresistant springs and permanent magnet/ferrous component interactionswithin this device with return it towards its contracted state if noother forces are applied.
 2. This device will be linked with otheridentical devices in order to create actuator chains. These chains willhave increased strength with the addition of each actuator component.These chains will be bundled together in an appropriate manner tofurther increase their contractile strength. Chains in each bundle maybe activated independently to allow for a fine degree of control ofcontractile strength.
 3. This device and its auxiliary arrangements(chains and bundles of chains) will be used in prosthetic devices,robotic devices or implantable applications. This device and itsauxiliary arrangements (chains and bundles of chains) will be fullyimplantable when encased in a biocompatible sheath. Said sheath willhave components to allow for the attachment of biological structures.Said sheath will allow for transfer of force from actuators and theirauxiliary arrangements to biological structures.
 4. Control systems forthis device will mimic those of natural muscle and be able to interpretcontrol signals from the body with only minimal augmentation. Minimalaugmentation is here defined as compiling and amplification ofbiological control signals. This device may receive computer generatedcontrol signals however, the generation of contractile force andduration of contraction within the device will still mimic biologicalstrength propagation and control mechanisms.